Hi Shane,
You asked about controllers for your motors. I'm not well up on this subject, but if you dont know the type used originally, then it might be best to go for the aftermarket 4QD type controller, as these can be 'Tuned' to your motors specific needs.
There are lots of posts on the forum about this type of controller, and how to set them up. I know they're a little pricey, but so are replacement motors if you fry them!
Have a good read through the posts, and take it from there.
As for the 'Sewing Machine Pedal' idea, it might work, but I would have thought that the 'Plunger Pot' might be over rated (being 240v) for your application, but again, I'm guessing.
I know I've not been much help, but someone will point you in the right direction I'm sure.
Keep Thinking,
Regards,
mark.